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Sept. 4, 1962
G. H. PERKINS ETAL
3,952,118
LOAD CELL AND COMBINATION THEREOF WITH STRETCH FORMING MACHINE
Filed Dec. 9, 1959
3 Sheets-Sheet 1
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IN VENTORS .
GZ'OEG'E l1’. PEEK/NS
BY
ROBERT E 05 MARC
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Sept- 4, 1962
G. H. PERKINS ETAL
3,052,118
LOAD CELL AND COMBINATION THEREOF‘ WITH STRETCH FORMING MACHINE
Filed Dec. 9, 1959
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5 Sheets-Sheet 2
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INVENTORJ.
620,965 H PEEK/NS
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Sept. 4, 1962
G. H. PERKINS ETAL
3,052,1 18
LOAD CELL AND COMBINATION THEREOF’ WITH STRETCH FORMING MACHINE
5 Sheets-Sheet 3
Filed Dec. 9, 1959
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INVENTORS.
GEORGE /-/. PEEK/N5
'EOBERT F.’ 06 MARCO
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United States Patent 0
3,052,] 18
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Patented Sept. 4, 1962
2
1
about an upright axis 3. The turntable 2 is driven
through a ring gear 4 coaxial therewith, a driving gear 5,
a reduced speed gear transmission 6, a secondary gear
transmission 7, and a pair of hydraulic motors 8 to which
pressure ?uid is supplied by a variable delivery pump 9,
driven by a motor 10, so that the speed of the table 2
can be accurately controlled.
Mounted on the frame 1 is a stretch forming piston
3,052,118
LOAD CELL AND COMBINATION THEREOF WITH
STRETCH FOlNG MACHINE
George H. Perkins, Euclid, and Robert F. De Marco,
Mentor, Ohio, assignors to The Cyril Bath Company,
Solon, Ohio, a corporation of Ohio
Filed Dec. 9, 1959, Ser. No. 858,376
8 Claims. (Cl. 73-141)
This invention relates to a load cell and stretch form
M‘
10
ing machine combination and particularly to a load cell
for the purpose of controlling the tension applied to a
length of stock being stretch formed about a rotary die.
One of the principal objects of the present invention
is to provide a load cell so mounted that it is main
tained substantially free ‘from stresses and strains of any
nature except those directed axially of the load cell
itself.
Another object is to provide a load cell comprising
two members movable relatively toward and away from
each other and so interconnected in spaced locations
along their length that they are constrained from move
ment relative to each other in all directions transversely
of their length, but ‘have negligible resistance to move
and cylinder assemblage 12 comprising a reciprocable
carriage 13 driven by a double ended piston 14 having
rods 15 and 16, respectively, and reciprocable in ‘a cylin
der 17. The ends of the rods 15 and 116 are ?xedly con
nected to the frame 1, ‘as indicated at 18 and 19. The
cylinder 17 is secured to the carriage 13 for movement
therewith longitudinally of the frame lvwith the cylinder
axis extending parallel to the path of movement of the
carriage.
In order to allow for any possible misalign- '
ment of the carriage and cylinder, the cylinder is con
nected to the carriage ‘for limited relative rocking move
ment to permit compensation for irregularities in the
carriage trackway.
For this purpose, a suitable bracket 20‘ is ?xedly con
nected to the cylinder 17 and through rods 21 is con
nected to a ?tting 22 which, in turn, is connected to the
ment for short distances in at least one direction length 25 carriage 13 so that at the point of connection of the car
riage and ?tting, they can rock relative to each other about
wise, and an elastically deformable load element oper
atively connected at its opposite ends to the members
horizontal axes.
so as to be deformed thereby upon relative movement
of the members in the one direction, with means at the
.
trackways 25 and 26 by means of rollers 27 and 28, the
The carriage 13 is mounted on the frame ‘on suitable
ends of the members for connecting the members to 30 rollers 27 rolling on top of the trackway 25 and rollers
‘force applying means of which the applied force is to be
sensed.
Another object of the invention is to provide a load
cell which is especially adapted for use in connection 35
with stretch vforming machines in which stock is stretch
formed about a side face die.
Still another object is to provide, in such a machine,
a stretch forming assemblage for stretch forming stock
28 rolling on the underside of the trackway 26, so as to
preventtilting of the carriage, about an axis extending
transversely of its path, by the longitudinal pull imposed
on the carriage by the stock being stretch formed.
In order to supply pressure ?uid to the carriage !13, so
as to yieldably resist'movement thereof toward the turn
table 2 during the stretch forming of the stock as it is
wrapped on the forming die, pressure fluid is supplied
from a source located on the carriage 113 and may com—
and a load cell so combined vas to provide advantages 40
prise a hydraulic pump 30 driven by a motor 31. The
in intensity of the signal obtained and to limit the sig
pump is connected to the cylinder 17 at opposite sides of
nals substantially to those due to components of force
the piston 14 through suitable conduits and a conven
parallel to the length of the load cell.
tional remote control reversing valve by which, in selected
Other objects and advantages will become apparent
positions, the ?uid supplied bythe pump 301 can'be sup
from the following description wherein reference is made 45 plied
to either end of the cylinder, selectively, or, blocked
to the drawings, in which:
so as to prevent supply of pressure ?uid to the cylinder
FIGS. 1, 2, and 3 are a top plan view, side elevation,
while connecting the ends of the cylinder to each other.
and a vertical sectional view taken on line 3-3 of
Since the cylinder is exceedingly long, it is desirable
FIG. 2, respectively, showing a stretch forming machine.
that it be supported ‘for movement longitudinally of the
and load cell combination of the present invention;
50 frame 1. For this purpose, the cylinder 17 is provided
FIG. 4 is an enlarged fragmentary top plan view of
at the end adjacent the carriage with a yoke 32 which,
a portion of the present machine with the load cell of
at its ends, has rollers 33 which ride on suitable track
the present invention installed;
ways 34 extending longitudinally of the frame. I At its
FIG 5 is a fragmentary enlarged side elevation of
opposite end, the cylinder has a roller 35 which is ar
the structure illustrated in FIG. 4, part thereof being
ranged to ride on a track 36 extending longitudinally of
shown in section for clearness in illustration;
the
frame. As mentioned, the piston rods -15 and 16 of
FIG. 6 is a vertical cross sectional view taken on the
the assemblage are ?xedly connected at each end to the
line 6-6 of FIG. 4; and
frame 1. Thus, by admitting ?uid pressure to opposite
FIGS. 7, 8, and 9 are vertical cross sectional views,
ends of the cylinder, the carriage 13 and cylinder 17 can
respectively, taken on lines 7——7, 8—8, and 9—9, re 60 be reciprocated as a unit lengthwise of the frame 1.
spectively, of 'FIG. 5.
For completing the stretch forming assemblage or ten’
Referring to the ‘drawings, the load cell is shown as
sion means, an elongated arm 40 is mounted upon the
combined with a stretch forming machine of a general
carriage for swinging about an axis parallel to the axis of
character shown in United States Letters Patent No.
the table. One end of the arm is connected to the car
2,514,830, issued to Cyril J. Bath on July 11, 1950, 65 riage 13 by an upright post 41 so that the arm can swing
but modi?ed to obtain the full advantage of the combina
about the upright axis of the post 41. The arm 40 extends
tion of a machine of this type with the present load cell.
from its pivotal connection with the post 41 back in the
The machine shown for purposes of illustration is one
direction toward the table ‘2 and is relatively long. At its
such as disclosed in the copending application of George
forward
end the arm 40 is supported on suitable slide
H. Perkins, Serial No. 792,304, ?led February 10, 1959, 70
pads 42 and 413, respectively, so as to relieve the arm from
now Patent No. 2,974,707, and comprises a longitudinal
binding stresses.
frame 1 on which a turntable 2 is mounted for rotation
$052,118
3
Further, positioning rollers 45 are arranged to reduce
friction and maintain the carriage in proper alignment
transversely of the frame 1.
Carried on the end of the arm 40 which is the nearer
to the table is a stretch forming head 46 adapted to engage
one-‘end of a length of stock for applying tension thereto
endwise. The arm 40 is movable along with the head
46 toward and away from the table 2 while such move
4
of sets of tie bolts, the tie bolts 58 of one set being ar
ranged in a rectangular pattern, one at each corner of
the arm 55, and the tie bolts 59 of the other set being cor
respondingly arranged. Since each of the tie bolts 58 is
arranged in the same manner as the other tie bolts 58 with
respect to the arms, and each tie bolt 59 is arranged in the
same manner as the other tie bolts 59 with respect to the
arms, only one of each set of tie bolts is described here
ment ‘is resisted by yieldable resisting force due to the
in in detail.
pressure ?uid supplied to the cylinder 17 from the pump 9. 10
Each tie bolt 58 is connected at its threaded lower end
Mounted on the table for movement therewith is a
clamp 47 which is adapted to engage the opposite end
of the stock and hold it in ?xed relation to the side face
60 to the lower ?ange of the arm 55 and extends upward
ly therefrom through a suitable passage 61 in the upper
?ange of one of the channels 5i)v of the arm 40, with
_
radial clearance. At its upper end the bolt carries a suit
‘In the stretch forming of the stock with the structure 15 able washer 62 which is disposed between the head 63 of
the bolt and the upper surface of the upper ?ange of the
above described, one end of the length of stock is secured
associated channel 50. Normally, when the arms are un
to the clamp 47 for rotation in ?xed position relative to
strained, the bolt 58 is preloaded and thereby under ten
the die D. The opposite end of the length of stock is
sion tending to urge the arm 55 upwardly. Thus, the arm
gripped by the head 46. Accordingly, when tension is
applied to the stock 8 by rotation of the table, the wrap 20 55 is urged upwardly by a similar bolt 58 arranged one
near each of the corners of the arm 55.
ping of the stock on the die D is opposed by the arm 40
Each of the bolts 59 is connected at its threaded lower
which-moves endwise relatively toward the table while
end 65 to the arm 40 and extends, with radial clearance,
being ;resisted by predetermined tensioning force as a
upwardly through a passage 66 in the lower ?ange of the
result of the assemblage 12. The arm 40‘ is elongated
and extends from its pivotal connection with the post 41 25 arm 55, through a passage 67 in the upper ?ange of the
arm 40, and through a passage 68 in the upper ?ange of
back toward the table 2 a substantial distance and, as
the arm 55. The bolt 59 carries at its upper end a nut
mentioned, the end of the arm ‘which is nearer the table
69 between which and the upper surface of the upper
is supported on suitable slide plates or skid plates 42
?ange of the arm 55, a suitable washer 70 is interposed.
and 43.
As disclosed in US. Patent No. 2,849,048, issued 30 Thus, when the bolts 59 are tightened and are under ten
sion, they urge the arm 55 downwardly at each of its four
August 26, 1948, it ,is desirable to control the tension
corners.
applied endwise of the stock to the stock by signals de
As mentioned, each of the bolts 58 has a screw threaded
rived from a suitable load cell responsive to the endwise
lower end 60 in engagement with the arm 55 and each
tension applied to the stock. Furthermore, it is desir
able that this load cell be subjected substantially only 35 of the bolts 59 has a screw threaded lower end 65 in
engagement with the arm 40. Further, the bolts have
to, forcecomponents directed endwise of the stock and be
welded
thereto, respectively, nuts 71 which are accesible
substantially free from any force components directed
die D.
transversely of the stock.
-
through windows 72 in the arm 40 so that the bolts can
be tightened readily to adjust their tension and to facilitate
For this purpose, the load cell of the present invention
is provided, the use of this load cell being made particu 40 installation.
By this arrangement the arm 55 is tensionally sus
larly eifective by the elongated arm 40. The speci?c
pended but is free to move axially or endwise a short
details of vthe load cell and arm are best illustrated in
distance by a transverse ?exure of bolts 58 and 59 and
FIGS. 5 through 9, to which reference is now made.
thus
without frictional resistance. Since this movement
J'The'arm 40 is an elongated rigid structure which may
very slight, the bolts offer substantially no resistance
be in the form of two oppositely facing channels 50 dis 45 is
to such ?exure.
posed with their‘open sides toward each other and held
Due to the clearance between the bolts 58 and arm 40
in' rigidly ?xed spaced relation to each other by suitable
at
the passage 61, and to the clearance between the bolts
tie bolts 51' and spacing sleeves 52, or otherwise. At the
59 and arm 55 at the passages 66 and 68, and between
end of the arm 40, attached to the post 41, the channels
50 are welded to a suitable sleeve 53. The arm is further 50 bolts 59 and arm 40 at the passage 67, neither the bolts
58 nor the bolts 59 can be placed under compression by
reinforced at the top by means of .a tie plate 54a which
movement of the arm 55 by extraneous forces in the
extends part .way from the sleeve 53 toward the free end
direction in which it is urged by the tension of the par
of the arm, and at the bottom by a plate 5412 which extends
ticular
bolt. Any tendency toward compression of the
the full length of the channel members 50. To the under
side of the plate 54b, near the free end of the arm, the 55 bolts 58 by lifting arm 55 is relieved by its head 63 being
lifted thereby from the arm 40. Any tendency toward
skid pad 42 is secured.
,
'
'
compression of the bolts 59 by pulling downwardly on the
‘ Carried on the arm 40 is a suspended arm 55 which is
arm 55 is relieved by its head 69 being lifted thereby
supported in laterally spaced telescopic relation to the arm
from the arm 55. Thus the arms 40 and 55 are held by
40 midway between its channels 50 by suitable tension
isolation supporting means which constrain the suspended 60 the bolts in tensioned equilibrium in their normal later
arm 55, from movement in all directions transversely
relative to the arm 40, but which permit the arm 55 to
move a limited amount lineally of the arms while resisted
ally spaced relation.
. Due to the side face of the die, the arm 40' often must
swing about the post 41 under the tension applied to the
stock to maintain its alignment With the stock, and hence
only by negligible ?exure of the supporting means and
while free from any frictional binding forces. The arm 65 lateral forces are imposed on the arm 55 which must be
55 is shown as a rigid Iabeam. A gripping head support
56.is rigidly secured to that’ end of the arm 55 which is
closer to the table and is adapted to support the stretch.
forming head 46. ‘ By this arrangement, any pull exerted 70
transmitted to the arm 40 Without imposing any stresses
on the load cell which is to be connected between the
two arms. For this purpose, transverse bolts 73 are
connected to the arm 55 at their inner ends and at their
onpthe stock is applied by the head 46 directly to the arm
55 and urges it generally endwise relative to the arms 40
outer .ends engage the outer faces of the channels 50.
These bolts likewise are placed under tension by pre
and 55.
loading and, since they extend directly transversely of
‘a
'
_ Aivery simple and effective tension isolation supporting
the arms, any forces applied tending to pull the members
means for providing this suspension comprises a plurality 75 55 laterally relative to the arm 40 are resisted by direct
3,052,118
5
tension on the bolts 73. The bolts 73 are readily ?exible
transversely of their axes. Thus the arm 55 is sub
stantially immovable transversely relative to the arm 40
but is readily movable endwise of the arm 40 by mere
?exure of the elongated bolts 58 and 59 and the small
diameter tie bolts 73, transversely of their axes.
In order to obtain a signal, a load cell is connected to
the arms 40 and 55 so as to be responsive to the relative
movement of the arms endwise. For this purpose, a
6
?ed patent, and which controls the supply of pressure
?uid to the stretch forming cylinder in accordance with
the re?ected signal in the manner set forth therein, and
thus maintains the desired tension on the stock.
Having thus described our invention, We claim:
1. A load cell comprising a pair of elongated rigid arm
members, tension isolation supporting means connecting
the members together at spaced locations along their
lengths in telescopic and laterally spaced parallel relation
block 75 is ?xedly connected to the arm 45 by heavy 10 to each other and constraining the members from move
ment relative to each other in all directions transversely
transverse pins 76 so as to be movable with the arm
40 as a unitary structure. The web of the arm 55 is
slotted endwise from its free end so as to provide clear
ance, as indicated at 77, between the block 75 and the
arm 55 so that there is no frictional engagement there
between.
The load cell or tension member 78 may be in the form
of a bar of metal of accurate cross section.
It is con
nected at one end by a pin 79 to the block 75 of the
of the lengths of the members while permitting them
relatively free movement relative to each other for short
distances lengthwise of the members, an elastically de
formable tension strain element operatively connected
at its ends to the members, respectively, so as to be
elastically deformed lengthwise of the members upon said
movement of the members lengthwise in one direction,
means at the ends of the members, respectively, for con
arm 40 and at the other end by a pin 80 to the arm 20 necting the members to force applying members so as to
55 near the support 56. As a result, any pull exerted
on the arm 44 by the stretch head 46 is transmitted to
the arm 40 through the load cell 78. The load cell is
relieved from any transverse and frictional forces due to
the bolts 58, 59, and 73. Accordingly, the load cell 78
urge the members lengthwise relative to each other in said
one direction, said tension isolation supporting means
comprising a plurality of elongated, relatively stiff, ten
sioning elements arranged in groups, one group near each
end of the telescoped members, the elements of each
group extending generally transversely of the length of
is responsive substantially only to tension forces di
the members, each element being operatively connected
rected endwise of the arms, and hence lengthwise of the
at one end to one of the members and at the other end
stock but is subject to the full lengthwise force because
to the other of the members, said elements being pre
the ?exure of the rods offers negligible resistancce.
30 loaded for applying axial tension directed transversely
As a safety precaution, in event of breakage of the
of the members in directions such that the components
load cell 78, an adjustable abutment in the form of a bolt
of tensioning force of the elements of each group hold
32 is threadably connected to a suitable sleeve portion
the members in tensioned equilibrium transversely of
83 ?xed on the arm 55 for movement with the arm 55.
This bolt is arranged so that its end facing toward the 00 On their lengths in the laterally spaced parallel relation of
the members, and constrain the members from substan
stretch forming head can engage the block 75 which is
tial relative movement transversely of their length under
connected to the arm 40 and thereby arrest movement
components of force extraneously applied to one of the
of the head and the arm 55 endwise relative to the
members transversely of the length of the members, and
arm 40. Since the normal relative movement of the
arms endwise, while the arms are connected by the load 40 each element having negligible resistance to ?exure a
slight distance transversely of its axis.
cell, are only a few thousandths of an inch, the bolt 82
2. A load cell according to claim 1 wherein all of the
is set so that the clearance between it and the block 75
elements are parallel to a plane normal to the lengthwise
is only slightly more than that amount of movement of
path of relative movement of the members.
the arm 55 endwise. Should the load cell break, there
3. A load cell according to claim 2 wherein said ele
can be little axial or endwise relative movement of the
ments are relatively stiif, straight, metal rods.
arms 40 and 55 before the bolt arrests the movement,
4. A load cell according to claim 1 wherein each group
thus relieving the parts from excessive impact stresses
comprises two sets of elements, and the axes of the ele
and strains.
In the form illustrated, a suitable tension device 85 is 50 ments of one set de?ne an upright plane, the axes of the
elements of the other set de?ne an upright plane parallel
connected to the load cell 78 and is responsive to the elon
gation of the load cell under stress and thereby re?ects
the tension being applied to the stock. The signal thus
to the ?rst mentioned plane and offset therefrom length
wise of the members, and the axes of the elements of one
set extend in a direction at right angles to the axes of
re?ected is an extremely accurate signal inasmuch as all
frictional binding forces are eliminated and the cell is sub 55 the elements of the other set.
5. A load cell according to claim 4 wherein the axes
jected to only true tension forces directed endwise of the
of the elements of said one set are upright and the axes
stock.
of the elements of the other set are horizontal.
Any forces transversely of the arms are initially greatly
6. A load cell according to claim 1 wherein at least
reduced because of the fact that the arm 40 is extremely
long and consequently any lateral forces applied to the 60 two elements of each group are upright, one for resisting,
by tension, movement of one of the members upwardly,
stretching head by the stock and tending to swing the
and the other for resisting, by tension, movement of said
arm 40 transversely have a substantial mechanical advan
one of the members downwardly, and the connection of
tage over the frictional forces imposed by the post 41,
each element to the members affords free axial movement
and hence can swing the arm readily, particularly as the
outer end of the arm is well supported on slip pads such 65 of the element relative to at least one of the members
when the members are moved by an extraneous force rela
as heretofore described. Thus binding stresses resisting
tive to each other in the direction in which urged by said
swinging of the arm also are greatly reduced.
element, whereby the elements operate free from axial
The strain gauge may be of the so-called patch type,
such as disclosed in United States Patent No. 2,849,048, 70 compression.
7. A load cell according to claim 6 wherein said one
issued August 26, 1958, identi?ed above, or it may be of
upright element is secured at its upper end to the upper
the transducer or other type.
portion of said one member and to the lower portion of
The signal derived from the signal device may be an
the other member, the other of the upright elements is
electric signal which, in turn, is fed to a conventional
tension control unit, such as described in the above identi 75 secured at its upper end to said other of the members
3,052,118
7.
8
and at its lower end to said one of the members, and
References Cited in the ?le of this patent
UNITED STATES PATENTS
each element is connected to at least one of its associated
members by extending through a passage therein and is
freely movable axially in the passage, and has a portion
1,5 80,430
2,445,682
2,645,935
resting against a face portion of said one associated mem
ber facing away from the direction of tension, and is free
for movement outwardly from said face upon release of
the tension.
8. A load cell according to claim 1 wherein each group
of the members for resisting, lby tension, movement of one
of the members upwardly, and two additional upright
elements spaced apart from each other transversely of the
members, and spaced endwise of the members from the
2,806,5 06
Yurka ______________ __ Sept. 17, 1957
2,844,027
Davie ________________ __ July 22, 1958
2,849,048
v Curtner ______________ __ Aug. 26, 1958
887,695
74,057
France ______________ __ Aug. 16, 1943
comprises two upright elements spaced apart transversely 10
?rst mentioned two members, for resisting, by tension,
movement of said one of the members downwardly.
Gaines ______________ __ Apr. 13, 1926
Macgeorge __________ __ July 20, 1948
Pramuk et a1 _________ .. July 21, 1953
FOREIGN PATENTS
Netherlands __________ __ Feb. 15, 1954
OTHER REFERENCES
15
Publication: “Aircraft Engineering,” Jan. 1952, page 5.
(Copy in 73-141.)